WHITESPACES: Wrap energy calculation and solve-call in the Mixed-Riemannian-TR solver in a try-catch statement

In case an error occurs while solving or calculating the energy, the program does not stop
but the error is handled in the Mixed-Riemannian-Trust-Region solver and the program continues
with a smaller trustregion-radius.

Apparently it is not used.

Up until dune-common 2.7, the Dune namespace contained shared_ptr:
First as an actual implementation, later simply as a namespace
import.  Dune-common post-2.7 has removed that import,
and users of shared_ptr really have to explicitly specify
the std:: namespace prefix.

This makes mixed-cosserat-continuum compile again.

The latter is deprecated as of dune-functions 2.6.

In particular, MonotoneMultiGridStep use shared_ptr much more
frequently now.  Also, various of its data members are now
protected, and getters/setters have to be used.

This leads to some simplification

This is an important step towards making the 'mixed' Cosserat code more like
the regular one.  The mid-term goal is to merge the two implementations, because
there is way too much code duplication here.

This makes 2nd-order orientation functions work again.

[[Imported from SVN: r10101]]

It appears that there may be very small energy increases due to
rounding errors.

[[Imported from SVN: r9867]]

[[Imported from SVN: r9860]]

[[Imported from SVN: r9858]]

[[Imported from SVN: r9857]]

[[Imported from SVN: r9856]]

'Mixed' means that the spaces for deformations and microrotations can
be chosen separately.

At this point there hasn't been a lot of testing yet.  In particular,
parallelizing the assembly is currently not supported.

[[Imported from SVN: r9852]]